Despite the utility of conventional neuroimaging (MRI and CT scanning), some diagnostic conundrums remain in the neurological disorders. We describe an optical diagnostic tool to extract biochemical information from neurological tissues using Frequency Domain Photon Migration (FDPM). This low-power laser device devised at the LAMMP has been used to study patients with brain tumors at UCIMC. We have characterized normal and abnormal neurological tissues in vivo during neurosurgery operations and located physiological differences between diseased and normal states, locally. This technique provides a non-invasive or minimally invasive adjunct to current neurological diagnostics and in the future, a functional monitor of neurological physiology.